protobuf: Update version from 2.4.1 to 3.1.0

We need to change the URL a bit:

In this release they didn't add a tar.bz2 format archive. The archives
automatically generated by github for the release dont exist in
.bz2 format - just zip and tar.gz

Morover, autotools fails for us for not yet clear reasons (configure not
run after autogen?).

Anyway, they added language variants including c++ in which
already include the configure script. So we take this.

protobuf.be0

@@ -1,6 +1,6 @@
 #!/usr/bin/env beesh
 
-# BEE_VERSION protobuf-2.4.1-0
+# BEE_VERSION protobuf-3.1.0-0
 
 ## this file was created by bee init and should be executed to build a
 ## bee-package. (Additional hints are located at the end of this file.)
@@ -9,7 +9,7 @@
 ## The source URL(s) define the location of the sources that will be
 ## downloaded. Version variables may be used to simplify reuse of this bee-file.
 
-SRCURL[0]="https://github.com/google/protobuf/releases/download/v${PKGVERSION}/protobuf-${PKGVERSION}.tar.bz2"
+SRCURL[0]="https://github.com/google/protobuf/releases/download/v${PKGVERSION}/protobuf-cpp-${PKGVERSION}.tar.gz"
 
 ###############################################################################
 ## Add URLs/pathes to patch files to the PATCHURL array.